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    <script>
        // 假值对象的布尔强制转换结果为true 
        var a = new Boolean(false);
        var b = new Number(0);
        var c = new String("");
        var d = a && b && c

        console.log(d);     // 返回的是一个String，长度为0
        console.log(Boolean(a))
    </script>
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